Disitamab Vedotin (RC48) in Hormone Receptor Positive, HER2-low Metastatic Breast Cancer (the Rosy Trial)

This study (the Rosy Trial) is testing a drug called disitamab vedotin (RC48), which is an antibody-drug combination that targets a protein called HER2, in women with breast cancer that has spread (metastatic) and has hormone receptor-positive, HER2-low expression — a subtype that may respond to this targeted approach. **You may be eligible if...** - You are a female patient aged 18–70 with metastatic breast cancer - Your cancer is hormone receptor-positive (ER and/or PR positive) and HER2-low (a specific level of HER2 expression) - You have already received hormonal (endocrine) therapy - You have at least one measurable tumor site or bone-only disease - Your general health and organ function are adequate **You may NOT be eligible if...** - You received chemotherapy, radiation, immunotherapy, or hormonal therapy within 2 weeks before joining - You had major surgery within the past 2 weeks - You have severe heart disease, including heart attack or stroke in the past year - You have an active autoimmune disease requiring treatment - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.